Electrical – 270v DC current limiting circuit

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I have looked through some of the current limiting responses, but don’t see any close to what I’m working on for my project.

I have an EV system running in around 200 – 270V DC. I want to build a circuit that will allow me to connect an external say 280V DC LiPeO4 battery bank and charge up the internal DC system.

Obviously, I don’t want to dump the total current possible when the circuit is made. I have a Gigavac high voltage relay that can make the circuit.

I want something that will limit the charge to say 20A at 270V DC to the internal battery system to ‘top it up’ in real time.

I’m an engineer but more in thermal/mechanical with some electrical background, but not in ICs or design.

Any help is appreciated, but remember to keep it simple (e.g. pretend I’m a 10yo) 😀

Best Answer

If you don't need an adjustable current limit value and you don't need to cut off all charging when a specific terminal voltage is reached, then the classic two-transistor circuit will work with appropriately beefy parts.

Current Limit circuit

At 20 A you'll dissipate about 14 W in Rsense, and much more in T1 depending on the initial terminal voltage. A switching circuit will be much more efficient, but also more complex.

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